The blockage of human arteries can lead to a variety of serious medical complications. This is so because arterial blockages reduce blood flow through the affected artery and may result in damage to the tissue that is relying on the blood supply. For example, if the blockage is in an artery which supplies blood to the heart itself, a heart attack may result.
Such arterial blockages, which are also called stenoses, are typically caused by the build-up of atherosclerotic plaque on the inside wall of an artery. In fact, several such stenoses may occur contiguously within a single artery. This can result in a partial, or even complete, blockage of the artery. As a result of the danger associated with such a blockage, several methods and procedures have been developed to treat stenoses. One such method is an angioplasty procedure which uses an inflatable balloon to dilate the blocked artery. A typical inflatable angioplasty device, for example, is disclosed in U.S. Pat. No. 4,896,669 which issued to Bhate et al. for an invention entitled “DILATION CATHETER”. The Bhate et al. angioplasty device includes an inflatable angioplasty balloon which is insertable into a peripheral artery of a patient for positioning across a stenosis. Once positioned, the angioplasty balloon is then inflated to flatten the stenosis against the inside wall of the artery thereby improving the blood flow through the artery.
Angioplasty balloons have enjoyed widespread acceptance in the treatment of stenoses. Recent studies, however, have indicated that the efficacy of the dilation of a stenosis is enhanced by first, or simultaneously, incising the material that is creating the stenosis. Consequently, recent developments have been made to equip angioplasty balloons with cutting edges, or atherotomes, which are intended to incise a stenosis during the dilation procedure. For example, the device disclosed in U.S. Pat. No. 5,196,024 to Barath entitled “BALLOON CATHETER WITH CUTTING EDGE,” which is assigned to the assignee of the present invention, is an inflatable angioplasty balloon having a number of atherotomes mounted longitudinally on the surface of the balloon.
Upon inflation of the Barath balloon, the atherotomes induce a series of longitudinal cuts into the surface of the stenotic material as the balloon expands to dilate the stenosis. As a result of such cuts, the stenosis is more easily flattened, and the likelihood of damaging the artery during dilation is reduced. Generally, however, the surface of a stenosis is bumpy and undulating, and contains numerous peaks and valleys. As such, incision of a stenosis with one long, continuous blade that is mounted on the surface of an angioplasty balloon can be uneven. Specifically, while the peaks of a stenotic surface may be effectively incised, incisions in the valleys present on the surface of the stenosis may be problematic. Thus, it can happen that only a small portion of the stenosis is actually incised. Furthermore, long, continuous blades reduce the flexibility of the catheter making it more difficult to guide the catheter through the vasculature of the patient.
In light of the above, it is an object of the present invention to provide a device for incising both the peaks and valleys of a stenosis in a vessel of a patient. It is a further object of the present invention to provide a blade unit for an angioplasty balloon having an effective cutting edge that substantially conforms to the surface of a stenosis when the balloon is inflated. It is still another object of the present invention to provide a device for incising a stenosis that is flexible enough to be easily guided through the vasculature of the patient to the site of the stenosis. It is another object of the present invention to provide a device for incising a stenosis in a vessel which is relatively simple to manufacture, is easy to use, and is comparatively cost effective.